1. Field of the Invention
The present invention relates to a drivability improvement technology for a motorcycle in which the front portion of the rear fork for supporting a rear wheel is mounted on the crankcase of the engine so as to be capable of swinging in the vertical direction.
2. Description of Background Art
A drivability improvement technology for so-called unit swing type motorcycles has been proposed, for example, the technology disclosed in JP-A-2-99481 entitled “FRONT AND REAR WHEEL STEERING APPARATUS FOR MOTORCYCLES”. The basic construction of technology is such that, according to FIG. 1 in the same publication, a bracket 8 is mounted on the rear arm brackets 7, 7, via cylindrical rubbers 21, 21, a rear arm 9 is mounted on the bracket 8, and a rear wheel 12 is mounted on the rear arm 9. In addition, as shown in the figure, since the resilient main shafts of the cylindrical rubbers 21, 21 are inclined with respect to the longitudinal centerline of the vehicle body, the resilient members (rubbers) of the cylindrical rubbers 21, 21 resiliently deform to swing the rear arm or the engine in the horizontal direction when the motorcycle is turned around. Thus, a cornering force is exerted on the rear wheel. (In the same publication, see page 4, from line 20 of the upper left column to line 5 of the upper right column).
As is clear from FIG. 1 in the aforementioned publication, in order to incline the cylindrical rubbers 21, 21, a bracket 8 having a complex shape is necessary. At the same time, the rear portions of the rear arm brackets 7, 7 inevitably become complex in shape.
In other words, in the technology disclosed above, since a bracket 8 which corresponds to a intermediate member is additionally required, the number of components increases correspondingly. Further, the structure from the rear arm bracket 7 to the rear arm 9 is upsized, making it difficult to make the vehicle body compact.
In addition, since the costs of the bracket 8 and the rear arm brackets 7, 7 are expensive, the price of the motorcycle increases correspondingly.